Do you know what kinds of metals can be used for Overlaying?

Overlay welding is a kind of technology that uses welding method to stack materials with certain properties on the surface of weldment. Its purpose is not to connect the weldment, but to obtain the deposited metal layer with special properties such as wear resistance, heat resistance and corrosion resistance on the surface of the weldment, or to restore or increase the size of the weldment. Surfacing method is widely used in manufacture and repair.

Metal for hardfacing

Generally speaking, the surfacing metal should first meet the use conditions of the weldment; secondly, the weldability of the surfacing metal should be considered, and then the more economical surfacing metal should be properly selected.

Common surfacing metals used under working conditions include: hypoeutectic cobalt base alloy and cobalt base alloy containing intermetallics are used for high stress intermetallics wear; low alloy steel for surfacing is used for low stress intermetallics wear; cobalt base alloy or nickel base alloy are mostly used for intermetallics wear + corrosion or oxidation; high alloy cast iron is used for low stress abrasive wear, impact erosion and abrasive erosion Low stress and severe abrasive wear, carbide for cutting edge; cobalt base alloy for cavitation erosion; high alloy manganese steel for severe impact; hypoeutectic cobalt base alloy for severe impact + corrosion + oxidation; hypoeutectic cobalt base alloy and cobalt base alloy containing intermetallic compound for intermetallic wear under high temperature; austenitic manganese steel for gouging abrasive wear; high temperature creep for thermal stability Cobalt base alloy carbide type cobalt base alloy is selected for variable strength (540 ℃).

Iron based hardfacing metal has many products, wide range of properties, good combination of toughness and wear resistance, and the biggest advantage is low cost, so it is widely used. There are four categories:

One is pearlitic steel hardfacing metal, which has good weldability, strong impact resistance and low hardness. It is mainly used to repair mechanical parts such as axle.

The other is austenitic steel surfacing metal. Austenitic manganese steel surfacing metal has the characteristics of high impact toughness and work hardening, but it is easy to produce hot cracks. It is generally used to repair the parts of metal to metal wear and abrasive wear under the severe impact load, such as mining stock, railway crossing, etc. Austenitic chromium manganese hardfacing metal has better weldability than austenitic manganese steel, as well as better corrosion resistance, heat resistance and heat crack resistance. It is mainly used to repair manganese steel and carbon steel parts suffering from severe impact.

The third is the martensitic steel hardfacing metal. The structure of this kind of hardfacing metal is mainly martensite. The hardfacing layer has high hardness and yield strength, high wear resistance, and can withstand medium impact, but its impact resistance is worse than that of pearlitic steel and austenitic steel. It is mainly used to repair parts worn between metals, such as gears, tractor chassis, etc.

The fourth is the alloy cast iron surfacing metal. This kind of surfacing layer has high abrasive wear resistance, heat resistance, corrosion resistance, good oxidation resistance, and can withstand light impact, but it is easy to crack during surfacing, and special care is taken during welding, mainly used for surfacing of agricultural machinery, mining equipment and other parts.

Ni cr-b-si series alloy is the most widely used in Ni based hardfacing metal. It has excellent resistance to low stress abrasive wear and inter metal wear. It has good corrosion resistance, heat resistance and high temperature oxidation resistance, but the resistance to high stress abrasive wear and impact resistance is slightly poor. It is usually used in corrosive medium or high temperature environment under low stress abrasive wear.

The nickel base alloy containing intermetallic compounds, such as ni-32mo-15cr-3si, has high hardness at high temperature, excellent resistance to intermetallic wear and medium abrasive wear, but poor impact resistance. This alloy is more suitable for gas tungsten arc surfacing or plasma arc surfacing, and is often used for surfacing the sealing surface of valves working in severely corrosive media.

The price of nickel base alloy containing carbide is much lower than that of cobalt base alloy. From an economic point of view, it has been widely used as a substitute for cobalt base hardfacing metal.

Cobalt based hardfacing metal, mainly refers to cobalt chromium tungsten alloy, which can maintain high strength and hardness at 650 ℃, has certain corrosion resistance and excellent adhesion and wear resistance. Among all kinds of hardfacing metals, cobalt based alloy has the best comprehensive performance, and is commonly used for surface hardfacing of parts in high temperature working state.

Copper based hardfacing metals are generally divided into four categories: bronze, brass, white copper and pure copper. Copper based hardfacing alloys have good corrosion resistance, cavitation resistance and wear resistance between metals. They can be made into bimetallic parts by hardfacing on iron-based materials, and can also be used to repair worn parts. However, copper based hardfacing metals have poor corrosion resistance, wear resistance and high temperature creep resistance, low hardness and are not easy to be welded It is only suitable for the environment below 200 ℃, this kind of surfacing metal is mainly used for the surfacing of bearing shells, sealing surfaces of low-pressure valves, etc.

Carbide hardfacing metal is mainly used in the case of severe wear, such as the hardfacing of oil well bits and road building machinery parts.